Function:
The function of the Digestive System is to break down food into component molecules, and make it so that these molecules can easily be absorbed and used in the body. This is made possible by a series of organs in the digestive track.
The Mouth:
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The Esophagus:
The Esophagus is a muscular organ that connects the mouth to the stomach. The food from the mouth moves through the esophagus by a series of muscle contractions, these muscle contractions are called Peristalsis. Peristalsis occurs in waves and pushes the food through the esophagus. There is a ring- like muscle in the esophagus that blocks the passage of the food from the mouth to the stomach. This muscle is called the lower esophageal sphincter. As the food approaches the lower esophageal sphincter the muscle relaxes and allows the food to pass into the stomach.
The Stomach:
The stomach is a hollow organ and one of its jobs is to store the swallowed liquids and foods. Another job is to physically break down the food into smaller molecules. This is done by the three layers of muscles lining the stomach, when these muscles contract the food is mixed up and broken down. As the muscles work to break down the food, they are also mixing the food with the digestive juices in the stomach. There are millions of glands in the stomach that secrete gastric juices that mix with the food. These gastric juices contain pepsin, which is an enzyme that breaks down proteins in the food. The food remains in the stomach for between two and four hours. Then it begins to be forced into the small intestine; at this point the food is about the consistency of tomato soup.
The Small Intestine:
The small intestine is a muscular tube that is about six meters long and 2.5 centimeters in diameter. It is here that the digestion is completed. The liquid food is mixed with more digestive enzymes and juices. The small intestine also has muscle contractions that further break down the food.
The small intestine has three parts, the duodenum, jejunum, and ileum. Most of the breaking down of the food takes place in the duodenum. Here the food mixes with enzymes secreted from the pancreas; these enzymes break down carbohydrates, fats and proteins. Also the food mixes with bile secreted from the liver. Bile is stored in the gallbladder, when food is consumed the bile is squeezed out of the gallbladder and through bile ducts into the small intestine.
The jejunum and ileum are where the nutrients from the food are absorbed into the circulatory system. Lining the intestinal walls are thousands of finger like structures called villi. Villi increase the surface area available to absorb nutrients; the process of absorption varies depending on the nutrient. The specialized cells of the villi diffuse molecules of nutrients in to the blood stream, this way the nutrients can be transported throughout the body.
Colon (Large Intestine):
The colon connects the small intestine to the rectum. It processes any waste that is left after all the nutrients are absorbed. Water and salts are absorbed into the intestinal wall while the waste is passing through the colon. This leaves only solid material. Vitamin synthesis also occurs in the large intestine, anaerobic bacteria synthesize some B vitamins and K vitamins. These vitamins are absorbed as needed into the body. The bacteria also help protect the digestive tract from harmful bacteria and infections.
Rectum:
The waste from the colon is released into the rectum, and it is the rectum that lets the brain know when it is necessary to use the restroom.
About the Picture:
It is a collection of photos that are of different things in nature. Leaves, flowers, berries, wood and pine needles. The photos were put together in Photoshop to make them look like an image of the digestive system.
About the Picture:
It is a collection of photos that are of different things in nature. Leaves, flowers, berries, wood and pine needles. The photos were put together in Photoshop to make them look like an image of the digestive system.
Sources:
- "Your Digestive System and How It Works." National Digestive Diseases Information Clearinghouse. Web. 15 Nov. 2010. <http://digestive.niddk.nih.gov/ddiseases/pubs/yrdd/>.
- "Center for Consumer Health Information, Cleveland Clinic." Cleveland Clinic. Web. 15 Nov. 2010. <http://www.clevelandclinic.org/health/health-info/docs/1600/1699.asp?index=7041>.
- "The Digestive and Endocrine Systems." Biology. the Dynamics of Life. New York: Glencoe/McGraw-Hill, 2004. 917-23. Print.